Debug: Docker container high memory usage

Docker container uses more memory than expected, gets OOMKilled, or host system runs low on memory.

Diagnose and fix container memory issues:

# 1. Check container memory usage
docker stats --no-stream

# 2. Check if container was OOMKilled
docker inspect <container> | grep -A5 'State'
# Look for OOMKilled: true

# 3. Check memory limit
docker inspect <container> --format='{{.HostConfig.Memory}}'

# 4. Profile memory inside container
docker exec <container> cat /proc/meminfo
docker exec <container> ps aux --sort=-%mem | head

# 5. Set memory limits
docker run -m 512m --memory-swap 512m myimage
# In Compose:
# deploy:
#   resources:
#     limits:
#       memory: 512M

Common causes:

• Node.js: Default heap is 1.5GB. Set --max-old-space-size=256
• Java: JVM doesn't respect cgroup limits by default. Use -XX:MaxRAMPercentage=75
• Python: Large dataframes in memory. Process in chunks
• File caching: Application caches grow unbounded. Set max cache size
• Log files: Logs written inside container accumulate. Use log rotation or write to stdout

Containers share host memory. Without limits, a single container can consume all available memory and affect other containers or the host.

Docker containers exceeding expected memory usage